Regarding to my sales calls this week, I met the client at American Express (Thai) Co., Ltd which might be potential for your hotel.
American Express (AMEX) is an American multinational financial services corporation headquartered in Manhattan. In each year, they have the visitors to Bangkok over 10,000 room nights and use the hotels in their preferred list. The staff/ guests can use the hotels outside the preferred list if those hotels accept the Amex card. If your hotel does accept the Amex card, please consider to offer the room rate for them kha.